HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 366
Tips & Tricks - CAS
UPC - 882780045217
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Tips & Tricks - CAS • In CAS, angles are always expressed in radians and no other setting is possible. When you are the calculator HOME screen, you can use the MODES view to change this default but this does not affect the CAS. • Step by step mode might appear to be quite useful for students but is quite limited in what it actually displays. Those hoping for the CAS to show complete working such as that required by a teacher will be disappointed. Choose Step by step mode to view some details of the calculations, displayed on the screen. After each step you are requested to press to proceed to the next stage. The alternative is Direct mode, in which only the result is displayed. • Incredible as it may seem, the CAS is capable of infinite precision when manipulating integers (memory permitting). To see this in action try evaluating 200 factorial and then press VIEWS. You can now scroll through all 375 digits of the result! • Don't use a summation variable of lower-case i. This is assumed by the CAS to be the unit imaginary value - the positive root of x2+1=0. • Although you can use the integration symbol provided on the keyboard it has disadvantages outlined on page 74. Use the INTVX function instead. See the example on page 339. • The COLLECT function referred to earlier will factorize over the set of integers. For example, COLLECT(x2-4) will result in (x+2)(x-2), whereas COLLECT(X2+4) will result in X2+4 back again. On the other hand the FACTOR function will factorize over the irrational and complex sets too. ( ) ( ) Entering FACTOR(X2+2) will result in the expression x + 2i x − 2i in complex mode. • The infinity symbol can be found in the Constants section of the MATH menu but can also be - obtained by pressing SHIFT 0. Pressing (-) first will produce ∞, while pressing (-) twice will give +∞. These are often needed for use in the LIMITS function. For example, evaluating LIMIT( x + x + x − x ,+∞) will give ½ (after a very long wait). As with the infinity symbol there is also a shortcut for the symbol i. Just press SHIFT 1. See page 333 for more keyboard shortcuts. 366